In this application, we have proposed two approaches to investigate the relationship between sudden infant death syndrome and sleep apnea. The first is research performed on infants, including normal controls, prematures, and infants with a "stopped breathing" episode. In these babies we will study the relationship between respiratory abnormalities and sleep. We will also define the type of respiratory abnormality that occurs, i.e. obstructive apnea and diaphragmatic apnea. The respiratory abnormality will also be correlated with secondary cardiac changes and oxymetric changes. Secondly, we have proposed research on adults and children to determine if there is a population "at risk" for either SIDS or sleep apnea. Two populations will be studied: 1) families in which a SIDS has occurred; and 2) families in which sleep apnea syndrome has been studied. In one of our cases of sleep apnea there was a direct relationship between these two populations. A study of a possible respiratory abnormality during sleep and the definition of this abnormality will be conducted in these two populations.